AMAZON spent $14.4 million (£11.5m) on “consultants” last year in a bid to block its US workers’ attempts to form a union, according to Labour Department information.

The union-busting efforts by the online retail giant cost the company more than three times the amount it spent in the previous year to try to stop workers from organising into unions at its warehouses across the country.

Nonetheless, last April, a warehouse in Staten Island became the first to form a union and gain the right to bargain a contract with the employer.

Amazon did manage to block attempts at other locations as the consultants helped persuade workers not to vote for a union.

A federal judge ruled in January that the company had violated employment laws by threatening to withhold wage increases if workers voted to form a union.

Amazon wrote in the filing that the consultants had been hired to aid the company in “expressing the company’s opinion on union representation and to educate employees about the issues, election process and their rights under the law.”

Under US federal law, companies are able to write off such costs as a business expense, meaning that taxpayers foot the bill for the anti-union consultants.